executor: panic on always false filter

[skyzh]

> select * from t where 1 = 0;
thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', src/array/data_chunk.rs:53:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[xxchan]

The panic's place changed.

> select * from t where false
thread 'tokio-runtime-worker' panicked at 'index out of bounds: the len is 0 but the index is 0', 
src/optimizer/plan_nodes/logical_projection.rs:66:25

---

Another issue 👇 this one is fixed in #561

>  select count(*) from t where false 
# What's this???
+-------+
| count |
+-------+
| 1     |
+-------+

[skyzh]

I suspect it's caused by the optimizer:

PhysicalProjection:
    InputRef #0
  PhysicalSimpleAgg:
      count(InputRef #0) -> INT
    Dummy:

The dummy executor should not return anything. However,

impl DummyScanExecutor {
    #[try_stream(boxed, ok = DataChunk, error = ExecutorError)]
    pub async fn execute(self) {
        yield DataChunk::single(0);
    }
}

[st1page]

I think the dummy executor should return nothing, but it should have schema... we need give Dummy Plan Node a schema when constructing it and implement fn schema(&self) -> Vec<ColumnDesc> for it

[skyzh]

Another problem is that,

> explain select 1
PhysicalProjection:
    1
  Dummy:

Projection is relying on Dummy executor to return a value... Maybe we should use ValuesExecutor for queries like select 1?

[xxchan]

We can create a new issue for dummy executor

[wangrunji0408]

Resolved as we already have a schema for all plan nodes.